Electric heating unit



March 6, 1962 L. c. HANSON ELECTRIC HEATING UNIT 2 Sheets-Sheet 1 IiVVENTOR. Iggy 6. 170223022 Filed March 24, 1960 March 6, 1962 c. HANSON ELECTRIC HEATING UNIT 2 Sheets-Sheet 2 Filed March 24, 1960 United States Patent Qfifice 3,024,345 Patented Mar. 6, 1962 3,024,345 ELECTRIC HEATING UNIT Leroy C. Hanson, Elmhurst, Ill., assignor to Ferro Corporation, Cleveland, Ohio, a corporation of Ohio Filed Mar. 24, 1960, Ser. No. 17,332 8 Claims. (Cl. 219-37) This invention relates to tubular sheathed electrical heating units of the type adapted for range surface heating and has reference more particularly to the facilities by which the tubular sheathed elements thereof are attached to an underlying supporting frame or spider, this application being a continuation in part of my pending application Serial No. 662,041, filed May 26, 1957, now abandoned.

In such heating units the tubular sheathed elements thereof are usually arranged in the form of a flat winding which is set in an opening of the range cooking top or in the opening of a mounting ring with the top face of the winding elevated slightly above the surrounding surface so that a cooking utensil will rest directly on the winding, and it is customary to provide a pan underneath the winding which serves not only to collect spillage but also as a reflector to direct heat upwardly to the bottom of the pan or utensil on the winding. This pan or reflector may be made as a part of the range top or of the mounting ring but generally is a separate part which may be removed for cleaning.

For supporting the coils of the winding above the pan, an open frame or spider is employed which permits spillage therethrough into the pan and also permits air circulation therethrough to the coils, and the frame or spider is commonly attached to the winding, and it is customary to mount the winding and attached frame or spider in the opening of the range cooking top or mounting ring so that it may be lifted up to provide access to the pan and to the frame or spider and the underside of the winding for cleaning thereof.

Various expedients have been employed to permit access to the pan and the underside of the heating unit for cleaning thereof, the heating unit being sometimes arranged for complete removal for this purpose, but generally it is preferred to hinge the heating unit at one side of the opening of the range top or ring so that it tilts to an upraised position at one side of the range top or ring opening to permit convenient access for cleaning or removal of the pan and for cleaning the underside of the heating unit itself.

In such heating units the end portions of the tubular sheathed elements of the winding are usually bent downwardly to a suitable level below the plane of the winding and extended outwardly through the side wall of the ring or pan so that they terminate at a protected place underneath the range top for connection of current supply conductors to terminal Wires which project from the ends of the tubular sheathed elements, and it is important that the place of connection of the current supply conductors with these terminal wires be arranged so as to be safeguarded against access of spillage or grease thereto as such spillage or grease at the terminal ends may cause current leakage or shorts to occur at the terminals or it may even migrate into the end of the tubular sheath and cause current leakage or shorts therein.

Because of the expansion and contraction of the coils of the winding on account of extreme temperature changes, it is important that the coils of the winding be attached to the frame or spider in a manner providing of FIG. 12.

relative movement of the coils on the frame or spider to permit such expansion and contraction thereon without affecting the certainty and permanence of the attachment of the winding to the spider and in accordance with the present invention this is accomplished by employing fasteners at appropriate places which are positively and permanently secured to the frame or spider and the coils and have suitable shape and inherent resiliency to accommodate themselves to the contraction and expansion of the coils which occurs in the temperature changes to which the heating unit is subjected.

The principal objects of the invention are to provide an improved tubular sheathed heating unit of surface heating type having a winding attached to a frame or spider; to provide an improved attachment of the winding to the spider; to simplify and facilitate the fastening of the winding to the frame or spider; to insure certainty and permanence of the attachment of the winding to the frame or spider with suflicient freedom of movement of the coils of the winding on the spider for expansion and contraction of the coils under temperature changes to which they are subjected; and to accomplish the freedom of relative movement by the shape and resiliency of the fastener itself without special or complicated construction of the parts to which the fastener is attached or tedious assembly procedure, these and other objects being accomplised as pointed out more particularly hereinafter and as shown in the accompanying drawings, in which:

FIG. 1 is a plan view of a heating unit assembly showing coil fasteners of this invention in single bend form;

FIG. 2 is an enlarged sectional view taken on the line 2-2 of FIG. 1 showing one of the coil fasteners;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2;

FIG. 4 is a plan view of another form of heating unit assembly employing coil fasteners of this invention of multiple bend form;

FIG. 5 is an enlarged sectional view taken on the line 5-5 of FIG. 4;

FIG. 6 is a sectional view taken on the line 6-6 of FIG. 5

FIG. 7 is a view similar to that of FIG. 5 but showing a modified double form of the fastener of FIG. 5;

FIG. 8 is a sectional view taken on the line 88 of FIG. 7;

FIG. 9 is a view similar to FIG. 5 but showing another form of the fastener of this invention;

FIG. 10 is a sectional view taken on the line of FIG. 9;

FIG. 11 is a view similar to that of FIG. 9 but showing a modified double form of the fastener of FIG. 9;

FIG. 12 is a fragmentary sectional view of a marginal portion of a heating unit assembly showing another form of fastener of this invention of a multiple bend form; and

FIG. 13 is a sectional view taken on the line 1313 For illustrative purposes, the invention is shown herein as embodied in a heating unit and mounting ring assembly 20 of a generally conventional type which is adapted to be mounted in an opening in the cooking top of an electric range in the usual manner.

The assembly 20 comprises a mounting ring 21 having a supporting spider member 22 pivoted or hinged at one side of the mounting ring, and arranged to carry spirally coiled heating unit means 23 that has the terminal ends 24 thereof associated with a terminal block 25, there being a heat reflecting and spillage collecting pan 26 supported in the mounting ring 21 in a position beneath the spider 22 and the heating means 23.

The mounting ring 21 has a generally horizontal annular flange 27 that is adapted to rest upon the cooking top (not shown), and at the inner edge of the horizontal flange 27 a downwardly extending substantially vertical annular wall 28 is formed, the lower end of which has a narrow inwardly extended horizontal support flange 29. The lower supporting flange 29 serves to support the pan 26, which has an annular flange or rim 30 that rests upon the horizontal flange 29 of the mounting ring. The pan is relatively deep, and has a sloping or conical surrounding wall, for reasons explained hereinafter, and at its rear side the pan 26 has a clearance opening 31 formed therein, this clearance opening being in the nature of a wide notch that extends to the upper edge of the pan, and provides clearance through which the terminal ends 24 of the heating means 23 may extend, and within which such terminal ends may move when the heating element is pivoted to its elevated position as described hereinafter.

The spider 22 is formed from a pair of sheet metal strips that have corresponding portions 32 between their ends fastened together by rivets 33 or in any other convenient manner, and at one end of the portions 32 the sheet metal members are bent to a diverging relationship to provide forward arms 34, while at the other or rear end of the portions 32 the sheet metal members are bent in a diverging relationship to provide diverging rear arms 35. The arms 34 and 35 are of such a length that the ends thereof may be located over the flange 29 so as to be supported thereon, it being noted however, that such support is in most instances obtained by resting on the flange of the pan 26 as will be evident in FIG. 1 of the drawings. At their outermost ends, the rear arms of the spider have integral extensions providing connector arms 36 that are bentso as to extend generally toward each other as shown in FIG. 1. At the inner ends of the connector arms 36 the sheet metal strips are bent into a spaced parallel relationship so as to extend rearwardly and provide hinge arms 37. The hinge arms 37 provide a portion of the hinge means whereby the spider 22 is pivotally hinged to the mounting ring 21, and in providing this hinged relationship the hinged arms 37 extend through spaced vertical slots 38 that are formed in the vertical flange 28 of the mounting ring. These slots have their opposite edges offset in opposite directions as shown more particularly in my aforesaid application Serial No. 662,041, to provide opposed arcuate bearing seats to receive and support the ends of a hinge pin 39. The hinge pin 39 extends at its opposite ends through pivot openings in the hinge arms 37 and the hinge pin is supported therebeyond in the bearing seats at the slots 33 and thus the spider 22 may be swung from its normal horizontal position to an upraised position.

The heating means 23, as illustrated herein, is made up of two elongated sheath type electrical heating elements 23A and 238 that are wound in a double flat spiral as will be evident in FIG. 1 with the coils of the elements 23A and 23B intercalated, and in the relatively large central space within the spirals an escutcheon plate 4i) is mounted on the spider 22. It is to be noted that the heating element 23A is formed with three coils and provides the inner and outer coils of the winding, whereas the heating element 2313 has two coils, both of which are intercalated between coils of the element 23A.

The heating elements expand and contract in the heating and cooling thereof, and because of the spiral form a slight radial expansion and contraction of the coils occurs, and it is important that the spiral elements be suitably mounted so that they are free to expand and contract in accordance with temperature changes.

To this end only the outer coil of each element 23A and 23B is attached to the spider 22 and only at places remote from the hinge 39 and the terminal ends 24. Thus the outer coil of each element 23A and 23B is secured to the forward arms 34 only of the spider as shown in FIG. 1.

For this purpose of securing these outer coils to the spider arms 34, wire fasteners are employed which are welded to the coils and to the spider arms at spaced apart places providing an intermediate portion of a resiliency to permit relative movement of the coils on the spider. Wire fasteners 41 of inverted L-shape may be employed having short upper arms 42 substantially paralleling the coils and welded to the underside thereof and having the legs 43 thereof welded near their lower ends to embossments 44 pressed from the spider arms 34, all as shown particularly in FIGS. 2 and 3.

The coil of the heating unit is fastened to the spider arm in a position in which it rests on the upper edge of the spider arm, and the spider arms 34 are of such flexibility that, although the heating elements 23A and 23B are securely attached to the spider 22, such increase and decrease in length of the coil between the two places of fastening thereof which occurs on account of temperature changes, is readily accommodated by the flexi bility of the arms 34, and any change in arcuity of the coil portion is accommodated by permissible twist or bending of the wire of the inverted L-shaped wire fasteners 41.

As will be evident in FlG. 1, the heating elements 23A and 23B are wound in a double spiral and at the outer ends of the spirals are bent downwardly as at 45 and are then bent outwardly at 46 to provide the relatively short terminal portions 24, and at the inner ends of the spirals the heating elements 23A and 23B are likewise bent downwardly as at 47 and then outwardly as at 48 to provide the relating long terminal portions 24 as shown in FIG. 1

The downwardly extending portions 45 and 47 are so related that the several terminal portions 24 may extend parallel to each other beneath the hinge 39 and toward the terminal block 25.

The heating elements 23A and 23B are of conventional form, each comprising a tubular metal sheath 49 containing a central helical resistance 50 which is embedded in heat conductive electrical insulating material 51, such as magnesium oxide powder, compacted to a hard dense mass which electrically insulates the resistance from the sheath.

The flat winding composed of the spiral portions of the heating elements 23A and 23B constitutes the active portion of the heating unit and accordingly the resistances 50 of the heating elements 23A and 2313, in accordance with conventional practice, extend to or into the downturned portions 45 and 47 where they are electrically connected to low resistance terminal conductors which extend therefrom out through the bends 46 and 48 and through the terminal portions and project from the sheath ends, as indicated at 52 for attachment of current supply conductors thereto.

The terminal portions 24 extend an equal distance outwardly under the range top (not shown) so as to terminate at a place where they are safely protected against spillage from cooking operations on the heating unit, and their outer ends are arranged to extend into pockets 53 of the terminal block 25 in which provision is made for connection of current supply wires to the exposed projecting ends 52 of the terminal conductors.

This terminal block 25 is of ceramic material and is formed with a bottom wall, from which side walls 54 and intermediate walls 55 extend upwardly from the bottom wall and all said walls 54 and 55 extend forwardly from a relatively thick rear or outer end wall 56 having openings 57 therethrough to accommodate current supply conductors.

Between the two intermediate walls 55 and between one of these walls 55 and one of the side walls 54, two small pockets 53 are formed to accommodate respectively therein terminal clips 59 and 6t and between one of said walls 55 and the other side wall 54 a large pocket 53 is formed to accommodate a large common terminal clip 61 therein, and each of said pockets has one of the openings 57 leading therefrom through the rear or outer end wall 56. The terminal clips 59 and 653 are associated respectively with the corresponding long ends 24 of the two heating elements 23A and 2313 which have the projecting terminal wires 52 thereof welded to the respective clips 59 and 60.

The other terminal clip 61 constitutes the common terminal for the two heating elements 23A and 23B as will be evident in FIG. 1 of the drawings, and the clip 61 is therefore connected to both of the terminal wires 52 of the other short ends 24 of the heating elements 23A and 23B. Three line wires 62 are shown and each extends through a respective one of the openings 57 through the rear wall 56 and said wires are secured to the respective terminal clips by screws 64.

For holding the terminal block on the outer ends of the terminal portions 24 and protecting the terminal block and terminal connections against grease and spillage, two inner end cover plates 63 of sheet metal are provided at the inner end of the terminal block and which conjointly extend substantially entirely across the inner end of the terminal block.

These plates 63 are alike, except that one has a ground screw 64 thereon, and one thereof is secured to the outer ends of the short terminal portions 24 which lead from the outer coils respectively of the spiral windings of the two heating elements 23A and 23B and the other is secured to the outer ends of the long terminal portions 24 which lead from the inner coils respectively of the spiral windings of the two heating elements 23A and 23B.

In the expansion and contraction of the heating elements under the changes of temperature to which they are subjected, the coils thereof tend to expand and contract and by reason thereof the terminal portions 24 at the opposite ends of each element tend to move toward and away from one another and as the corresponding ends of each heating element 23A and 23B tend to move similarly in this manner the two short terminal portions 24 which are connected to the one plate 63 tend to move similarly toward and away from the long terminal portions 24 which are connected to the other plate 63 and thus by employing separate plates 63, expansion and contraction of the coils is accommodated and each element 23A and 23B is free to expand and contract.

Moreover the pockets 53 in which the terminal clips 59, 60 and 61 are located are of sufiiciently greater width than the clips located therein so that these clips are free to move sidewise in their pockets to permit freedom of expansion and contraction of the coils of the elements 23A and 23B.

The plates 63 are located quite close to one another, substantially as shown in FIG. 1, when the heating elements 23A and 23B are at normal room temperature and separate to some extent when the heating elements 23A and 23B are energized, and the terminal block 25 is attached to the ends of the terminal portions 24 and to the plates 63 in a manner to permit such relative movement of the plates 63 with respect to one another and corresponding movement of the ends of the terminal portions 24 which are attached to the plates.

The plates 63 are permanently secured to the respective pairs of terminal portions 24 in a manner to provide a sealed connection which will preclude passage of grease or spillage therethrough, and for this purpose the terminal portions 24 pass through plate openings which have annular flanges 65 projecting therefrom which are staked onto the sheaths of the terminal portions 24 or welded thereto to fixedly secure the plates 63 to the terminal portions 24 and provide a leak-proof connection.

Greater flexibility of the coil fasteners to accommodate twisting strains and to permit sliding movement of the coils lengthwise and transversely of the spider arms at the places of fastening may be provided by employing fastener wires of additional length with added bends between the places of welding thereof to the spider arm and the heating unit coil, examples of which are shown in FIGS. 4 to 13 inclusive.

Referring first to FIG. 4, which shows a heating unit and mounting assembly, the mounting ring 66 and pan 67 and terminal block 68 thereof are of substantially the same construction as in FIG. 1 and the terminal 5 stems of the heating unit winding are connected to the terminal block and provided with terminal wires and clips contained in pockets of the terminal block as in FIG. 1.

The spider, which is indicated as a whole at 69, is composed of a center strip 70, which extends diametrical 1y from front to rear of the opening in the ring 66, and has a pair of opposite side strips 71 secured centrally thereto, and the forward end of the center strip 70 and outer ends of the side strips 71 are supported on the o-utturned margin of the pan 67 which in turn rests on the inturned bottom ledge of the upright annular wall 72 of the ring 66 to support the spider in the same manner as the spider is supported in FIG. 1.

At its rear end, the center strip is pivoted to a bracket 73 which is attached to the upright annular wall 72 of the ring 66 so that the spider 69 and heating unit winding thereon swing to an upraised position at the rear of the ring, and at its forward end the strip 70 may have a nose portion 74, such as shown in FIG. 12, which snaps under a latch 75, or as shown in FIG. 12, it may snap into an opening 76 in the upright annular wall 72.

The heating means 77 of FIG. 4, like that of FIG. 1, is composed of two elongated tubular sheathed elements 77A and 77B wound in a double flat spiral with their coils intercalated, each however having two coils instead of two and three coils respectively as in FIG. 1, and these coils of the elements 77A and 77B are attached to the arms of the spider 69 by wire fasteners 78 and 79 which are illustrated in detail in FIGS. 5, 6 and 7, the inner coil of each element 77A and 7713 being connected to a separate one of the strips or arms 71, each by a fastener 78, and the outer coils of both elements 77A and 77B being conjointly connected to the forward end portion of the center strip 70 by a fastener 79, all as shown in FIG. 4.

Each fastener 78, as shown more particularly in FIGS. 5 and 6, is composed of a length of wire which is bent approximately at its midlength to provide two legs 80 and 81 disposed substantially at right angles to one another, and each leg 80 and 81 has an end portion of the wire bent laterally therefrom, both preferably in the same direction, to provide arms 82 and 83 extending substantially at right angles from the outer ends respectively of the legs 80 and 81.

FIGS. 5 and 6 show the fastening of the inner coil of the element 77B to its supporting spider arm 71, and as shown therein, one of the fastener arms, for example, the arm 83, is welded as at 84 to the side of the spider arm 71 so that it extends substantially horizontally therealong with its leg 81 extending upwardly along the side of the spider arm 71 and positioned so that the top leg 80 and arm 82 are at the proper level for fastening the inner 77B coil to the spider arm 71, and with the legs 80 and 81 offset laterally from the 77B coil with the bottom apex portion of the coil sheath extending crosswise over the arm 82 distantly from its leg 80 and at that place of crossing, the arm 82 is Welded as at 85 to the bottom of the inner coil of element 778.

The inner coil of the element 77A is in like manner fastened to the other arm 71' of the spider, and it is to be noted that each fastener 78, while providing a perma nent attachment of the heating element coil to the spider arm, is formed with three approximately right angled bends and four angularly disposed leg and arm portions between the places of welding to the spider arm 71 and to the coil of the respective element 77A and 7 7B, thereby providing substantial length of wire and bendable disposition thereof for yieldability to permit any movement of the coil which may be caused by expansion and contraction of the coils of the heating element.

The fastener 79, which is shown in FIGS. 7 and 8, is in effect a double form of the fastener 78 having right and left hand fasteners 78 joined by a common wire connector portion 86 which is welded centrally as at 87 to the side of the center strip 70 of the spider with the opposite end portions thereof serving as the bottom arms 83 of the two thus connected fasteners 78, each of which has legs 80 and 81 and a top arm 82, which are inturned toward one another and properly spaced by the common connector 86 so that they extend respectively underneath the adjoining outer coils of the two elements 77A and 778 to which they are respectively welded at 85.

Thus each outer coil of the elements 77A and 77B is permanently attached to the center strip 70 of the spider with the same yield'ability to permit movement of the respective coil, as in the case of the fastening of the inner coils by the fasteners 78.

Another form of coil fastener is shown in FIGS. 9 and and comprises a length of wire bent in S-shape with top and bottom arms 88 and 89 respectively disposed in generally parallel relation to one another and each having a return bend 90 at one end with intermediate portion 91 of the Wire connecting the return bends to one another.

The bottom arm 88 of this fastener is welded as at 92 to a spider arm 93 so that the fastener leans outwardly and upwardly at a slope, as indicated in FIG. 10, and has the upper arm 80 thereof extending crosswise under the heating element coil 94 and welded thereto at 95.

A double form of the fastener of FIGS. 9 and 10 is shown in FIG. 13 in which two fasteners of the FIGS. 9 and 10 form have a common connecting wire portion 96 providing conjointly the bottom legs 89 of the two fasteners and centrally welded at 97 to a spider arm 98, with the top legs 38 of the two fastener par-ts welded at 99 to adjoining heating element coils 100 and 101 in the same manner as in FIGS. 9 and 10.

Another form of coil fastener is shown in FIGS, 12 and 13, which, like the fastener of FIGS. 5 and 6, is a length of wire bent to provide legs 102 and 103 disposed substantially at right angles to one another, the upper one 102 of which has an arm 104 bent laterally therefrom at its outer end and extending transversely under and is welded as at 105 to a heating element coil 106 in the same manner as the arm 82 of the fastener of FIGS. 5 and 6 is welded to the heating element coil.

The other leg 103, however, which extends downwardly along the side of the spider arm 107 is looped at its lower end to form a U-shaped return bend 108 with an upwardly extending leg 109 which is welded approximately at its midlength to the side of the spider arm 107.

Preferably the spider arm 107 is provided along the lower portion thereof with an embossment providing a rib 110 at one side to which the upwardly extending leg 109 is welded, as indicated at 111 in FIG. 13, and the leg 103 extends divergently away from the side of the spider arm as shown in FIG. 13.

While I have shown and described my invention in a preferred form, I am aware that various changes may be made therein without departing from the principle of the invention, the scope of which is to be determined by the appended claims.

What I claim is:

l. A tubular sheathed embedded resistor heater having coils thereof distributively arranged in the form of a flat winding, the coils of which expand and contract in the plane of the winding according to changes of temperature thereof, a skeleton type frame underneath and supporting the winding and having arms with upwardly presented edges across which the coils extend transversely and upon which the coils rest slidably for movement thereon in the expansion and contraction thereof by said temperature changes, and fastening means by which the winding is attached to the frame with permissible freedom of slidability of the coils on the arms for expansion and contraction thereof, the fastening means comprising a wire which is fixedly secured permanently at spaced apart places therealong respectively to one side of an arm of the skeleton frame and to the bottom of a coil which rests on and extends transversely across the upwardly presented edge of that arm, the said wire having the length thereof between said spaced apart places in excess of the distance therebetween and bendably and twistably responsive to the expansion and contraction of the coil to which it is attached to permit sliding movement of said coil on the upwardly presented edge of the arm to which it is attached.

2. A tubular sheathed embedded resistor heater as de fined in claim 1 in which the said length of wire is formed with a bend with legs extending therefrom at an angle to one another and leading respectively to the spaced apart places at which the wire is fixedly secured permanently to the side of the arm and to the bottom of the coil.

3. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire is formed with a plurality of bends at spaced apart intervals between the spaced apart places at which the wire is fixedly secured permanently to the side of the arm and to the bottom of the coil.

4. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire is formed with a bend from which two leg portions extend, one of which said leg portions extends downwardly along said one side of the arm of the skeleton frame and the other of which said leg portions extends laterally from said arm at the top thereof.

5. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire is formed with a bend from which two leg portions extend, one of which said leg portions extends downwardly along said one side of the arm of the skeleton frame and the other of which said leg portions extends laterally from said arm at the top thereof, and each leg portion has a portion of said length of wire at the outer end thereof extending laterally therefrom to one of the spaced apart places where the length of wire is fixedly secured permanently to one side of an arm of the skeleton frame and to the bottom of a coil.

6. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire has laterally spaced generally parallel portions disposed respective ly at said spaced apart places and said portions extend angularly from the respective outer ends of two leg portions of said length of wire which are disposed at an angle to one another.

7. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire is formed with a bend from which two leg portions extend, one of which said leg portions extends downwardly along said one side of the arm of the skeleton frame and the other of which said leg portions extends laterally from said arm at the top thereof, and the leg portion which extends downwardly along said one side of the arm of the skeleton frame terminates in a return bend having an upturned portion which is fixedly secured permanently to said arm and the leg portion which extends laterally from said arm at the top thereof has a laterally bent portion at the outer end fixedly secured permanently to the bottom of the coil.

8. A tubular sheathed embedded resistor heater as defined in claim 1 in which said length of wire is formed in a general S-shape and extends divergently outward from an arm of the skeleton frame and at the top and bottom of the S-shape is fixedly secured permanently respectively to the bottom of the coil and to the side of said arm.

References Cited in the file of this patent UNITED STATES PATENTS 2,725,456 Weyrick Nov. 29, 1955 2,881,302 Ammerman Apr. 7, 1959 2,943,178 Aldous June 28, 1960 

